Navy Circumference Body-Fat Calculator
The exact Navy tape method, reused here as a consistent cross-branch estimate of body-fat %.
Estimate body-fat % with the exact U.S. Navy circumference formula (neck + waist; hips for women).
Result
About this calculator
Estimates body-fat percentage with the U.S. Navy circumference method, using neck (and waist; hips for women) measurements.
The formula
Navy method: men BF% ≈ 86.010·log10(waist−neck) − 70.041·log10(height) + 36.76; women add a hip term. Keep units consistent (inches or cm).
Frequently asked questions
Q: How accurate is it?
A: Typically ±3–4 percentage points versus a DXA scan. Treat it as an estimate, not a lab measurement.
Q: Why include hip for women?
A: The Navy formula uses hip circumference for female measurements to account for fat distribution.
Q: What is a healthy range?
A: Roughly 10–20% for men and 18–28% for women is considered fit; your service uses its own official tables.
How to read the result
A circumference estimate is a model rather than a measurement. The Navy equation was derived by fitting tape readings against a reference method across a large sample, so it reproduces the average relationship rather than the composition of any single person. Expect roughly three to four percentage points of error against a laboratory standard, and expect that error to grow for anyone whose fat distribution sits far from the average the equation was built on.
Technique moves the result more than most people expect. The neck tape goes below the larynx and slopes downward at the front, the waist tape sits at the navel, and for women the hip tape is taken at the widest point. A single inch of error on the neck measurement shifts the estimate by about a percentage point, which is how the same person can be measured twice and receive two different answers. Track change over time with one method and treat a comparison between two different methods as meaningless.
Military body-fat limits (secondary evaluation)
Under the 2026 rules, body-fat is the secondary evaluation when WHtR is at or above the gate. Maximum allowable body fat by branch, sex, and age:
| Branch | WHtR gate | Age bands | Max % BF (M / F) |
|---|---|---|---|
| Army | < 0.55 | 17–20 · 21–27 · 28–39 · 40+ | 20 / 30 · 22 / 32 · 24 / 34 · 26 / 36 |
| Navy | < 0.55 | 18–21 · 22–29 · 30–39 · 40+ | 22 / 33 · 23 / 34 · 24 / 35 · 26 / 36 |
| Air Force | < 0.55 | All ages | 26 / 36 |
| Marine Corps | < 0.52 | 17–26 · 27–39 · 40–45 · 46+ | 18 / 26 · 19 / 27 · 20 / 28 · 21 / 29 |
| Coast Guard | < 0.55 | Under 30 · Under 40 · 40+ | 22 / 32 · 24 / 34 · 26 / 36 |
| Space Force | < 0.55 | All ages | 26 / 36 |
DoD Instruction 1308.03 corridor: no branch stricter than 18% (men) / 26% (women), none looser than 26% / 36%. Firefighters and police have no federal body-fat limit.